I suggest you ...

Comparable to the described problems in this post https://onedrive.uservoice.com/forums/262982-onedrive/suggestions/17864110-enable-sync-client-to-allow-editable-synching-of-t the NGSC is not able to sync libraries (neither SharePoint nor O365-Groups), that have secondary versions turned on. The synced files are write protected and can’t be edited by library owners or other write-permitted users.
This really restricts the possibilities in scenarios where companies use the secondary-versioning and publishing-to-full-version-feature to secure the presentation of content in document libraries and keep content-producers productive.

Here we are months later, and the latest news is "not only are we not fixing it, we are making it so that you can no longer use the old client which you were using as a workaround also".

Checking in and out documents and having extra metadata are some of the best features in SharePoint. I'm glad that you are giving us an option to opt-out of the change that permanently removes the old client that allowed this functionality, but it sounds like doing that also means that we are opting out of updates for the NGSC, which works GREAT for OneDrive.

Why do we have to lose one functionality in order to have another? Why can't we have a great OneDrive sync experience AND retain some of SharePoint's best features?

Just identified very similar contraints and lost some hours understanding what was going on. Not documented properly anyway.
Microsoft you really ought to change from "Thinking about it" to "Implementing". This lack of 'coordination' between your tools are killing their core purpose. OneDrive and SharePoint cannot live without each others in many use cases.

Here is the feedback report I have made via the OneDrive client:
As an IT Staff member I want to report what I consider as an anomaly.

In my case I activated the Minor/Major Versioning settings together with the option Draft Item Security to “Only users who can edit items”. Deactivating the later would bring back the Synced OneDrive folder back to editable mode.

I tell you: this is not acceptable. You must find a solution to have your tools working together, not introducing constraints to each others. I must be able to hide the draft version to the "standard" audience on my SharePoint library for obvious reasons, AND i must still have access to the file in my OneDrive for edition.
In the same veins, I must be able to activate Checkout required option, and been able to trigger checkout of a document either from my OneDrive folder of from the edition apps (Excel, Word, Etc). As a reminder the later was possible not so long time ago.

Hi Douglas, it has been three months since your response. Can we get an update? We keep discovering new ways the need to run both the old and the new sync client blocks the collaboration that is supposed to be the core purpose of SharePoint.

This month's exciting discovery: there is NO prior sync client (groove.exe) for Macs. Since we have to keep SharePoint set to NOT use the new client so that the majority of our staff can use check-in/check-out functionality that we've relied upon for years, the Mac people don't have a sync client at all.

I can't wait to see what we find next month.

Some indication that Microsoft didn't remove functionality and then abandon its users would be appreciated.